Here are some interesting ones:
Adobe Flash, which was the only way to provide some smooth interaction on the web, no longer exists, thankfully. Now we have to develop on three different platforms with entirely different programming models in order to provide the same level of interaction.
We don’t use IRC for communication anymore. We prefer a bloated version called Slack because we just didn’t want to type in a server address.
Since we have much faster CPUs now, numerical calculations are done in Python which is much slower than Fortran. So numerical calculations basically take the same amount of time as they did 20 years ago.
Storing passwords in plaintext is now frowned upon, but we do it anyway.